Dynamoelectric machine



NOV. 12, 1940. R, M HEENTE 2,221,707

DYNAMQELECTRC MCHNE Originali Filed Nov. 55, 193@ 2 Sheets-Sheet l Nov.12, 1940. R. M. HEIN-rz DYNAMOELECTRIC MACHINE Original Filed Nov. 5,1958 2 Sheets-Sheet 2 AC LOAD Razn/7 M. )Ve/)772 Patented Nov.v l2, 1940UNITED STATES PATENT OFFICE Ralph M. Heintx, Montclair, N. J., assignerto Bendix Aviation Corporation, South Bend, Ind., a corporation ofDelaware Original application November 5, 1938, Serial No. 239,091.Divided and this application May 27,

1939, Serial Nol 276,197

3 Claima- (Cl. 171-321) This invention relates to a combined startingand generating unit for use with internal combustion engines and capableof functioning, first, to start an internal combustion engine byapplication of torque thereto, and thereafter to convert the powerdeveloped in the engine into electrical energy available for radiotransmission and other purposes requiring alternating current of high,low or intermediate frequency and/or potential.

An object of the invention is the provision of a dynamoelectric machineof novel construction permitting most advantageous use thereof formultiple purposes including, for example, the initial "turning over," orcranking, of an internal combustion engine, and the subsequentgeneration oi' alternating current of high frequency, by conversion ofmechanical energy transmitted thereto by way of said internal combustionen gine.

Among the novel features of the machine here- .in disclosed there isincluded that of a commutator adapted to be engaged by rotatablebrushes, for transmission of current between the former and the latterat relatively low rotor speeds, the invention further including theconcept of a novel method of manufacturing said commutator, and a novelmounting and mode of operation for said rotatable brushes, as a resultwhereof the said brushes remain in engagement with the commutator tofeed low voltage direct current to the stator windings during theduration of the engine cranking operation, but move out of engagementand thereby discontinue such direct current ilow as soon as the enginecrank shaft accelerates sufnciently to render further crankingunnecessary. Thereafter the stator serves solely as a supply ofalternating current for outside points of distribution and consumption.

These and other objects and features of themvention will become apparentupon consideration of the following detailed description, and uponreference to the accompanying drawings illustrating the preferredembodiment of the invention. It is to be understood, however, that thedrawings are illustrative only, and that the I'claims at the conclusionof the specification, rather than the drawings, measure the scope of theinvention.

- In the drawings, wherein like reference char acters refer to likeparts throughout the several views:

Fig. 1 is a longitudinal sectional view of a hous- "lll ing enclosing amachine embodying the invention, 'some of the enclosed parts being shownin section and some in elevation;

Fig, 2 is a diagram of the electrical connecvtions for the machine ofFig. l, and including a schematic representation of the speed responsivebrush shifting means.

Fig. 3 is a view showing part of the commutator and one of the brushesdisengaged therefrom (the engaged position being shown in Fis. l):

Fig. 4 is a view of the metallic annulus that eventually becomesthecommutator, as said annulus appears at an intermediate stage ofmanufacture;

Fig. 5 is a view of one of the insulating segments as it appears at thetime of insertion into the metallic annulus of Fig. 4; and

Fig. 6 is a transverse view of a section of the completed commutator.

In the drawings reference character Il designates a source oi' directcurrent (battery, for example) and Il designates an alternating currentreceiving apparatus, such as radio transmitters, transformers,receivers, rectiilers. motors. etc., to which alternating current ofhigh frequency may be supplied upon rotation, at relatively high speed,of an engine driven dynamoelectric machine whose rotor shaft i 2 isshown as directconnected to the crankshaft I3 of an internal combustionengine (not fully shown). Engines of a character adapted to drive highfrequency alternators are commonly employed on aircraft as a powersupply means for operation of electrical equipment of which the' 1unitsabove enumerated may be taken as examples.

Buch aircraft installations ordinarily include a battery such as thatshown at Il, charged sufflc/iently to energize the rotor and statorwindings it and i1, respectively, for use as a starting motor in theinitial cranking and acceleration of y the engine crank-shaft il toself-sustaining speed; Attainment of this normal running speed producesa centrifugal force of sufficient mag-V nitude to raise rotor brushesIl, Il, II, and 2l out of contact with commutator 23, whereupon `thepassage of current therebetween is interrupted. Thereafter statorwindings I1 serve 'solely as a source of alternating current, to be fedto the A. C. load il by way of multi-phase conductors 2l, 2l, and 2l.

of said brushes being in turn connected with collector ring 3l ofpositive polarity while the other two connect with collector ring Il ofnegative polarity. Brushes 3l. mounted in brush assemblies secured tothe housing 4I by suitable means (of which that shown at 42 in Fig. 1 isan example) engage collector ring 34; while brushes I1, correspondinglymounted, engage collector ring 8l. Conductors and Il complete theconnections from battery Il to the stationary brush sets, while aconductor 20 connects each of the rotating brushes Il to 2| with itscorresponding collector ring.

As hereinabove indicated, the stationary commutator assembly is made ina novel manner. including (as a step in the process) the union of twoannular metallic members 23 and 21, of which the former eventuallybecomes the segmented commutator, per se, while the latter is thesupporting core that is eventually secured to the housing by suitablemeans 29. A molding compound 3l) is the uniting element for parts 23 and21. the latter being provided. if desired, with compound receiving holes41 to insure more complete union therebetween.

A preceding step in the process is to cut slots I (Fig. 4) extendingpart-way through the metallic annulus 23, and spaced around the innerperiphery thereof, in accordance with a predetermined formula. toprovide pockets for receipt of segments l (Fig. 5) of mica or equivalentinsulating material. The annulus 23 (after union with core 21 in themanner above described) is machined down to finish shape (Fig. 6), inwhich process all metal located beyond (and, if desired, additionalmaterial within) the radially outermost part of the mica Segments 50(see line Il, Fig, 4) is removed. thus exposing the mica edges to view,at the outer side, and likewise resulting in the creation of acorresponding number of spaced conducting segments to constitute thecommutator. As shown each segment thereof has a nnal shape as indicatedat I2 in Fig. 6, and each of said segments has now become electricallyseparate from every other metallic part.

By this process of fashioning the commutator segments in situ, and froma single piece of metal, there are eliminated all problems of accuratetltting and positioning of segments individually;

each segment is automatically caused to appear in its proper relativeposition, since all remain unshiftable from start to finish of theprocess.

In order to offset any tangling tendency, as between the conductors I!and the rotating brush assemblies, I provide radially extending ribsforming pockets 40 in the housing l I, along which pockets theconductors I are run, and to which they may be secured, thus preventingtheir dropping inwardly into contact with the brush assemblies il to2l.4

This application is a division of my co,

pending application Serial No. 239,091 filed November 5, 1938.

What I claim is:

l. The method of making a commutator of the molded type, in which thesuccessive conducting segments are fashioned out of a single metallicannulus, which method includes the steps of cutting slots at spacedangular intervals along the inner side of the metallic annulus,inserting sheets of insulation in said slots, uniting saidsheet-containing annulus to a metallic cylindrical core by placing amolding compound therebetween and causing said compound to unitetherewith, and thereafter removing all that part of the metallic annuluswhich is disposed beyond the reach of said insulating sheets.

2. A dynamoelectric machine having commutator segments having smoothouter surfaces for engagement with the commutator brushes and alsohaving inner surfaces of corrugated contour, and a supporting coreintegral with said segments, said supporting core having an inner partof metallic material and an outer part of nonmetallic material, thesurface of said outer part being united with the inner corrugatedsurface of each commutator segment.

3. The method of making a commutator of the type in which the successiveconducting segments are fashioned from a single metallic annulus, whichmethod includes the steps of cutting slots at spaced angular intervalsalong the inner side of the metallic annulus, inserting insulationmaterial in said slots, uniting said insulation-containing annulus to acylindrical core, and thereafter removing all that part of the metallicannulus which is disposed beyond the reach oi' said insulation material.

RALPH M. HEINTZ.

